Re: SMP/cc Cluster description

David S. Miller
2001-12-06T20:18:11Z

From: Larry McVoy <lm@bitmover.com>
Date: Thu, 6 Dec 2001 12:10:04 -0800

Huh? Of course not, they'd use mutexes in a mmap-ed file, which uses
the hardware's coherency. No locks in the vfs or fs, that's all done
in the mmap/page fault path for sure, but once the data is mapped you
aren't dealing with the file system at all.

We're talking about two things.

Once the data is MMAP'd, sure things are coherent just like on any
other SMP, for the user.

But HOW DID YOU GET THERE? That is the question you are avoiding.
How do I look up "/etc/passwd" in the filesystem on a ccCluster?
How does OS image 1 see the same "/etc/passwd" as OS image 2?

If you aren't getting rid of this locking, what is the point?
That is what we are trying to talk about.